The optical transmission systems have evolved from past coarse wavelength division multiplexing (CWDM) to today's dense wavelength division multiplexing (DWDM). Recently, a more flexible and effective network architecture, called elastic optical network (EON), was proposed to provide higher transmission capacity and better meet ever-increasing traffic demand. Further, EON provides high spectrum efficiency by reducing the granularity of frequency spacing and improves flexibility in spectrum allocation for optical channels.
However, the compatibility between the current DWDM optical network and the EON is still a challenging issue. To enable today's DWDM optical network to evolve to EON, it is required to upgrade DWDM network hardware, such as reconfigurable optical add/drop multiplexer (ROADM), and to adopt expensive wavelength selective switches for flexible grid, resulting in increased EON construction costs. Meanwhile, in a case that an optical channel service requires a low optical bandwidth, a large amount of guard band overhead is apt to be generated, resulting in reduced spectrum efficiency.